Effect of thermal characteristics on distortion in laser cladding of AISI 316L

In laser cladding process, the inhomogeneous temperature distribution and the rapid thermal cycle can lead to accumulation of thermal distortion and dimensional errors. The mechanism of thermal distortion during the cladding process is not clear. The purpose of this study is to in-situ monitor the temperature by IR camera and thermocouples and to correlate the extracted thermal characteristics to the distortion of the parts during laser cladding of AISI 316 L. Experiments were conducted to investigate the effect of laser power, scanning speed, powder feeding rate and substrate thickness on the distortion. The distortion rate was acquired from the overall distortion curve. Results showed that the distortion rate did not change with scanning speed. Process thermal characteristics, including spatial temperature gradient and heating area, were extracted from the thermal signatures. The multiple sensor monitoring and extraction algorithm can provide a clear view of the whole part in three directions during the process. The temperature gradient of the parts was a complex vector field when variable process parameters were chosen. Both the temperature gradient and the heating area had an effect on the magnitude of distortion. An analytical model considering the influence of the heating area was applied to predict the angular distortion.